JP2929883B2 - Fail safe device for auxiliary air control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fail-safe device for adjusting an auxiliary air flow of an engine when a flow control valve fails.

[0002]

2. Description of the Related Art A failure may occur in an electric actuator for adjusting a flow rate of intake air, and there is a method for coping with the failure (see Japanese Utility Model Application Laid-Open No. 62-119446).

[0003] This will be described with reference to FIG.
When a large-capacity flow control valve 3 for adjusting the auxiliary air flow rate bypassing A and 1B is provided and the step motor type control valve 3 does not follow the command value from the control unit 5 due to failure, the driver May be generated in excess of the required torque.

In order to avoid this, a flow restricting valve 15 is provided in series with the flow control valve 3. The restriction valve 15 is of a hot water wax type, and has a large opening at a low water temperature and a small opening at a high water temperature. For this reason, when the required air amount during idling after warm-up is small, the large-capacity control valve 3
May be fully opened due to a signal line short circuit, etc., after warm-up, only the flow rate controlled by the restricting valve opening at high water temperature flows through the auxiliary air passage 2, thereby increasing the engine speed. It is not to be overkill.

[0005]

However, in the conventional apparatus, since the flow rate of the control valve 3 is restricted by the restriction valve flow rate at high water temperature, the adjustment range of the auxiliary air flow rate is increased. Can not. Further, the cost is increased by the provision of the flow rate restriction valve even though it is for fail safe.

[0006] Therefore the present invention is to determine whether any defect to the flow control valve, by failure performs fuel cut, and allows the use of large flow control valve without providing a flow restriction valve While the actual flow should be from the reference flow
The purpose is to maintain almost the same idle speed regardless of the degree of the rotation .

[0007]

According to a first aspect of the present invention, as shown in FIG. 1, an auxiliary air passage 22 bypassing an intake throttle valve 21 and an auxiliary air flow rate flowing through the passage 22 are adjusted according to a command value. A flow control valve 23, a means 24 for controlling a command value to the control valve 23 in accordance with an operating condition, a sensor 25 for detecting an opening degree of the throttle valve 21, a sensor detection value and the control valve 23 Means for calculating the total flow area Aa of the intake pipe from the command value to the engine, means 27 for calculating the reference flow rate Pqmax from the total flow area Aa, and means for measuring the intake air flow rate of the engine (for example, air flow). Meter or intake pipe internal pressure sensor) 28, means 29 for calculating the fuel injection amount based on the measured value, and the control valve 23 receiving the measured value Qs of the intake air flow rate and the reference flow rate Pqmax. And determining means 30 whether any defect, failure of the control valve 23 from the determination result inhalation
The measured value Qs of the air flow deviates from the reference flow Pqmax
As the size becomes larger, the number of cylinders for cutting off the fuel supply from the fuel injection valve 31 is increased, and a means 32 for driving the fuel injection valve 31 in accordance with the fuel injection amount when no failure occurs is provided.

In the second invention, as shown in FIG. 12, an auxiliary air passage 22 that bypasses the intake throttle valve 21, a flow control valve 23 that adjusts the flow rate of the auxiliary air flowing through the passage 22 according to a command value, and Means 24 for controlling the command value to the control valve 23 in accordance with the operating conditions, a sensor 25 for detecting the opening of the throttle valve 21, and the sensor detection value and the command value to the control valve 23. Means 26 for calculating a total flow area Aa of the intake pipe, and a reference flow rate Pq from the total flow area Aa.
means 27 for calculating max, means for measuring the intake air flow rate of the engine (for example, an air flow meter or an intake pipe internal pressure sensor) 28, and a measured value Qs of the intake air flow rate
Means 41 for calculating the ratio G between the reference flow rate Pqmax and the reference flow rate Pqmax
Means 42 for determining whether the ratio G is smaller or larger than a predetermined value (for example, 6); means 43 for setting the gain Qmxg according to the ratio G when the ratio G is smaller than the determination result; Means 44 for calculating a maximum value Fqmax from the gain Qmxg and the reference flow rate Pqmax.
Means 45 for comparing the maximum value Fqmax with the measured value Qs of the intake air flow rate, and, based on the comparison result, when the measured value Qs of the intake air flow rate exceeds the maximum value Fqmax, it is based on the maximum value Fqmax. Means 4 for calculating the fuel injection amount based on the measured value itself when the measured value Qs of the intake air flow rate is equal to or less than the maximum value Fqmax.
6, when the ratio G is smaller than the predetermined value, the fuel injection valve 31 is driven in accordance with the fuel injection amount. When the ratio G is larger than the predetermined value, the fuel supply from the fuel injection valve 31 is cut off. Means 47 for performing the operation.

A third invention is the second invention, wherein the ratio G
The number of cylinders from which the fuel supply is cut is increased as the value becomes larger.

[0010]

[Function] A large-capacity control valve 23 which has been close to the fully closed state until then.
However, when the signal line is kept open at the fully open position due to the short circuit of the signal line, the measured value Qs
Is the reference flow rate P according to the command value to the control valve and the throttle valve opening.
Since it is larger than qmax, it is determined that the control valve 23 has failed to increase the flow rate, and the intake air flow rate
The measured value Qs deviates from the reference flow rate Pqmax and increases.
The more the number of cylinders from which fuel supply is cut, the greater the number of cylinders . Due to the fuel cut at the time of the control valve failure, the torque generated in the engine is reduced, the generation of torque exceeding the driver's demand is prevented , and the flow rate must be within the reference flow rate Pqmax.
The engine speed is kept almost the same regardless of the amount of displacement .

[0011] Since such a fail-safe at the time of failure of the control valve is dealt with in the fuel control, the restriction valve for the flow rate becomes unnecessary, and when the restriction valve disappears, the large-capacity control valve 23 is normally operated to the full capacity. It can be used and the control range of the intake air flow rate is expanded.

In the second invention, the ratio G represents the degree of deviation of the measured value Qs of the intake air flow rate from the reference flow rate Pqmax. When the ratio G is smaller than a predetermined value, the fuel cut is performed instead of the fuel cut. When the injection amount is limited, the variation of the engine rotation becomes smaller in the region where the ratio G is small than in the first invention.

[0013] In the same way, even when the ratio in the third aspect of the present invention G is a lot number of cylinders to cut the fuel supply as large, approximately the same engine speed regardless of the ratio G obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
A large-capacity flow control valve 3 is provided in the auxiliary air passage 2 that bypasses the intake throttle valves 1A and 1B. In the step motor type control valve 3, a step motor 3a with a built-in valve is used.
Is the command value (electric signal) from the control unit 5
To move the valve 3b in the axial direction by rotating the valve 3b in the axial direction (as the valve 3b moves to the left in the figure, the control valve passage area becomes smaller) to adjust the auxiliary air flow rate. The control valve 3 is not limited to a step motor type, but may be a proportional solenoid type.

At the time of feedback correction of the idle speed, the actual speed is set to the target value (cooling water temperature, elapsed time after starting,
It is determined from a battery voltage, an air conditioner switch, the gear position of an A / T vehicle, etc.) to a constant value (for example, 25
(rpm), the control valve flow path area is returned to the target value by increasing and correcting the flow path area.

The conditions for entering the feedback correction of the idling speed are as follows: <1> idling, <2> low vehicle speed or neutral position, and if any one of them is released. Then, the feedback correction is stopped.

For this reason, various signals required for controlling the idle speed are input to the control unit 5. The main input signals are a rotation speed signal (1 ° signal) from the crank angle sensor 6, a wall temperature signal (a signal corresponding to a cooling water temperature) from the wall temperature sensor 7, and a throttle valve position signal from the throttle sensor 8. , Vehicle speed signal, air conditioner switch signal,
Neutral switch signal, power steering switch signal, battery voltage, and the like.

On the other hand, from a fuel injection valve 4 provided at an intake port of each cylinder, fuel is supplied to each cylinder at a rate of once per two engine revolutions and in a fixed cylinder number order according to a command from a control unit 5. (For example, in the case of a V6 engine, the fuel supply is performed in the order of 1-2-3-4-5-6), but the fuel supply is cut off during deceleration. Stopping fuel injection during engine braking suppresses HC emissions and reduces fuel consumption. Further, the rotation decreases due to the fuel cut at the time of deceleration and a constant value (1
When the speed becomes 400 rpm or less, re-injection is performed. At high vehicle speed (about 180 km / h or more), during overspeed (about 6300
約 6500 rpm), and the fuel cut may be performed at a vehicle speed of 0 km / h.

The signals required for fuel supply control and fuel cut during deceleration are based on the above signals (revolution speed, water temperature, throttle valve position, vehicle speed, battery voltage signals) as well as a reference from the crank angle sensor 6. Position signal (120 ° signal), intake air flow rate signal from air flow meter 9, O ₂ sensor 1
An air-fuel ratio signal from 0, a key switch start signal, and the like.

FIG. 3 is a flowchart for calculating the fuel injection pulse width Ti, which is executed at regular intervals (every 10 ms).

First, the output Qa of the air flow meter is set to A / D
Conversion is performed to obtain the intake air flow rate Qs, and the engine speed N is read (step 1 in FIG. 3).

From the intake air flow rate Qs and the number of revolutions N, the basic injection pulse width Tp is calculated as follows: Tp = K × Qs / N (1) where K is a constant expression based on the injection valve flow characteristics. The fuel injection pulse width Ti given to the valve 4 is Ti = 2 × Te + Ts (2) Te = Tp × Coef × (α + αm) × K _FC (3) where Te; effective pulse width Ts; invalid pulse width Coef; And the various correction coefficients α; air-fuel ratio feedback correction coefficient αm; air-fuel ratio learning control coefficient K _FC ; fuel cut coefficient (steps 2, 3 in FIG. 3).
4).

If the injection order is not sequential but simultaneous injection, then Ti = Te + Ts (2-1) instead of equations (2) and (3) Te = Tp × Coef × (α + αm) × K _FC (3) The fuel amount corresponding to Ti given by the equation
It is sufficient to supply each cylinder simultaneously once per revolution.

(1) to (3), (2-1), (3-1)
It is also known as a formula. For example (3) and equation (3-1) is a fuel cut coefficient K _FC for a K _FC = 0 and the value of the K _FC = 1 otherwise when the fuel cut. When the fuel is cut, the injection valve 4 is not opened even when Ts is output (that is, no fuel is supplied), and when the recovery condition is satisfied, re-injection is performed with K _FC = 1.

Subsequently, it is determined whether or not the fuel cut at the time of deceleration is to be performed, and the result is stored in a flag Fccyl (step 5 in FIG. 3).

This flag Fccyl is set for each cylinder and for 1
In the flag assigned to each bit, a bit value of "0" means that fuel cut is performed, and a value of "1" means that fuel cut is not performed. For example, when a four-cylinder engine is shown for simplicity, when "1" and "0" are arranged as shown in FIG.
The fuel cut is performed in the second and fourth cylinders. At the start of the fuel cut, the fuel cut cylinders are first halved, and all the cylinders are cut immediately to improve the feeling during deceleration.

When the large-capacity control valve 3 deviates from the command value due to a failure and is fully opened, a torque exceeding the driver's demand is generated.

To cope with this, in this example, the control valve 3
It is determined whether or not a failure has occurred, and a fuel cut is performed in the event of a failure.

First, a table containing the contents shown in FIG. 4 is retrieved from the throttle valve opening degree Tvo to obtain the throttle valve passage area Atvo and FIG. 5 from the number of steps to the step motor 3a (command value to the control valve). A table as the contents is searched to determine the control valve flow path area Aisc, respectively, and the sum of these is entered into a variable Aa (steps 6, 7, 8, 9 in FIG. 3). The variable Aa (= Atvo + Aisc) represents the total flow area of the intake pipe.

The number of steps to the step motor 3a is calculated by an idle speed control routine (not shown) different from that of FIG. If the control valve 3 is a proportional solenoid type, the control valve passage area Aisc is obtained from the on-duty given to the control valve.

The throttle valve opening Tvo is detected by the throttle sensor 8.
When the output variation is large, fully closed position learning may be employed, and the difference between the output when fully closed (ie, the fully closed position learning value) and the A / D conversion result may be used as Tvo.

The total flow area Aa is calculated as Pqmax = Aa × KAQGIN # (4) where KAQGIN #; area → flow rate conversion coefficient is converted into an air flow rate unit (step 1 in FIG. 3).
0). The reference flow rate Pqmax in the equation (4) is obtained by calculating the intake air flow rate at the time of sonic operation.
g, 25 ° C.) means a flow rate determined by the flow path area Aa and no longer flowing.

From the reference flow rate Pqmax, a gain G is obtained as follows: G = Qs / Pqmax (5) (Step 11 in FIG. 3).

From equation (5), the gain G is the ratio between Qs (actual flow rate) and Pqmax (that is, the flow rate that does not flow through the intake pipe any more if the control valve opening is equal to the command value). If in the atmosphere, G as long as the control valve is normal
Does not exceed 1.0. If the value is much larger than 1.0, it means that the actual flow rate of the control valve 3 is very large regardless of the command value from the control unit 5 to the control valve 3. It means that it is. That is, in this state, the control valve 3 has failed in the opening direction due to a short circuit or contamination of the signal line. The value of the gain G indicates whether or not a failure has occurred in the control valve 3, and the magnitude of the value of G indicates how much the actual flow rate Qs departs from the reference flow rate Pqmax.

A table is retrieved from the gain G to set a cylinder for performing fuel cut. In addition to the above-described fuel cut during deceleration, a fuel cut when a control valve fails is added. Again, for simplicity, FIG. 6 shows a four-cylinder example,
The horizontal axis of the table is G, and the vertical axis is the cylinder number.
This is given for each bit, "0" is fuel cut,
“1” is assigned as no fuel cut.

As shown in FIG. 6, if the value of the gain G is large, the actual flow rate is larger than the required air flow rate determined by the total flow area Aa. To go. Conversely, when the value of G is small (G ≦
2), since the control valve 3 is normal, all the cylinders are "1" (that is, all the cylinders have no fuel cut).
By providing the gain G with hysteresis, the hunting of rotation can be reduced.

The result of searching the table of FIG. 6 (that is, the set of bits for each cylinder) is moved to the flag Ffcccyl and stored (step 12 in FIG. 3). For example, 2 <G ≦ 3
In this case, the contents of the flag Ffcccyl are as shown in FIG.

Further, in order to ensure consistency with the above-described fuel cut during deceleration, two flags (Ffccyl and Fccy) are used.
The AND of 1) is taken, and the result is stored in another flag Fcflg (step 13 in FIG. 3). The reason for making the AND is to inject fuel when fuel cut during deceleration is not required and fuel cut when control valve failure is not required. Select a cut.

Finally, the fuel injection pulse width is output for each cylinder in accordance with the value of each bit assigned by the flag Fcflg (step 14 in FIG. 3). For the cylinder having a bit value of “0”, K _FC of the above equation (3) is set to K _FC = 0, and Ti (= T
s), and the cylinder of “1” outputs Ti with K _FC = 1.

Here, the operation of this example will be described.

Under the feedback correction condition at the time of idling, the opening of the control valve 3 is reduced and the minute flow rate is adjusted.

If the control valve 3 is kept open at the fully open position due to a short circuit of the signal line or the like at the time of this feedback correction, the actual intake air flow rate Qs obtained from the output of the air flow meter is equal to the command value to the control valve 3. And the reference flow rate Pqmax according to the throttle valve opening degree Tvo, it is determined that the control valve 3 has failed to increase the flow rate, and fuel cut is performed. Due to the fuel cut at the time of the failure of the control valve, the torque generated in the engine is reduced, and the rise of the idle speed is suppressed.

Similarly, even when the control valve 3 is suddenly opened during running other than at the time of idling, the fuel cut is performed as a failure of the control valve 3 so that unnatural acceleration feeling is not accompanied. Is done.

Further, the fail-safe function at the time of failure of the control valve is an arithmetic function in the control unit and is dealt with by fuel cut. Therefore, unlike the conventional example, it is not necessary to provide a flow rate restriction valve. When the restriction valve is gone,
Under normal conditions, the large-capacity control valve 3 can be used to its full capacity. That is, since the control range of the intake air flow rate is widened by using a large-capacity control valve, the present invention can be applied not only to idle rotation control but also to other controls requiring a large air flow rate. For example, in a lean burn engine,
At the time of switching from the stoichiometric air-fuel ratio to the lean-side air-fuel ratio, an increase correction of the auxiliary air amount is performed so that the torque does not change discontinuously before and after the switching, but in this torque control at the time of switching the air-fuel ratio, In the control for preventing the influence on the vehicle driving force due to the switching of the accessories, the flow rate can be adjusted with a margin.

Further, if it is only necessary to determine whether or not the control valve 3 has failed, the gain G can be compared with a predetermined value. However, in this example, the number of fuel cut cylinders is changed according to the value of the gain G. As shown in FIG. 6, as the value of the gain G increases, the number of fuel cut cylinders is increased by one, so that the value of the gain G (ie, the degree of deviation of the actual flow rate Qs from the reference flow rate Pqmax) is substantially increased. The same idle speed can be maintained.

FIGS. 7 to 9 show another embodiment, in which the intake air flow rate Qs obtained from the air flow meter output is set according to the flow path area of the intake pipe together with the fuel cut when the control valve fails. If the maximum value is exceeded, this maximum value is Qs
In this limited range, variations in idle rotation are suppressed, and an increase in engine rotation and unnatural acceleration sensation are prevented.

FIG. 7 is a modified example based on the configuration of FIG. 3. After the A / D conversion of the air flow meter output Qa and the reading of the rotation speed N, the flag is changed from the A / D conversion of the throttle valve opening signal. The processing up to Ffcccyl is performed first (steps 21 to 28 in FIG. 7). The contents of the processing up to this point are the same as those of the previous embodiment.

Thereafter, a process of limiting the intake air flow rate to the maximum value Fqmax unique to this embodiment is performed (steps 29 to 32).

From the reference flow rate Pqmax to the maximum value Fqmax
Fqmax = Pqmax × Qmxg (6) where Qmxg; gain (step 30 in FIG. 7). When the actual intake air flow rate included in the variable Qs exceeds the maximum value Pqmax, the variable The maximum value Fqmax is reset to Qs (steps 31 and 32 in FIG. 7). Since the value of Qs is subsequently used to calculate the basic injection pulse width Tp (step 33 in FIG. 7), when Qs> Fqmax, the maximum value Fqmax
It is limited to the supplied fuel amount calculated from the above. Qs
If ≦ Fqmax, Qs does not change.

The gain Qmxg in the equation (6) is not a constant value, but is obtained by searching a table containing the contents of FIG. 9 from the gain G (step 29 in FIG. 7).

In FIG. 9, the value of the gain Qmxg is constant in a region where the value of the gain G is small, but in a region where the value of G is large, the gain Qmx increases as the value of G increases.
The value of mxg is increased. As described above, the reason why the value of the gain Qmxg is increased in accordance with the value of G is that, for example, when the control valve 3 is fully opened and fixed in a region where the throttle valve opening is small, the air-fuel ratio is excessively shifted to the lean side to cause lean misfire. This is to prevent this lean misfire since the rotation occurs too much. In other words, the characteristics of the curved portion in FIG. 9 are experimental examples in which the upper limit of the idle speed is kept constant even when the deviation from the control valve flow rate corresponding to the control valve command value changes. In other words, in the range of G ≦ 6, even if the fuel cut is not performed, the idling rotation can be kept constant by limiting the supplied fuel amount. Therefore, step 28
Used in the control (flag Ffcccyl when control valve fails)
Table used to determine the value of G) is G as shown in FIG.
When ≦ 6, the value of the bit is set to “1” for each cylinder so that no fuel cut is performed. This point is different from FIG. This is because, if G ≦ 6, the fuel cut is performed while the fuel supply limit is to be dealt with, but the fuel limit is affected (that is, control interferes).

On the other hand, when G> 6, a fuel cut is taken as in the previous embodiment (as shown in FIG. 8, the greater the value of the gain G, the greater the number of cylinders in the fuel cut).
Therefore, in the region of G> 6, as shown in FIG.
The value of g is constant.

Note that, from the calculation of the basic injection pulse width Tp to the determination of the fuel cut during deceleration (steps 33 to 3 in FIG. 7).
6), AN of two flags, Ffccyl and Fccyl
The D processing (step 37 in FIG. 7) and the output processing of the fuel injection pulse Ti (step 38 in FIG. 7) are the same as those in FIG.

FIG. 10 shows that the control valve opening is forcibly changed regardless of the calculation result (specifically, the control valve command value) by the control unit 5 (the flow rate at the forcibly changed control valve opening). Is the flow rate of the forced control valve on the horizontal axis in FIG. 10), and shows the characteristics of the idle speed in the case of failure.

For comparison, the example of FIG. 3 is also shown in an overlapping manner. In the example of FIG. 3, the rotational speed is saw-toothed with respect to the forced control valve flow rate. This is because, in the example of FIG. 3, when the number of fuel cut cylinders is increased by one, a torque step is generated corresponding to the torque that should have been generated in that cylinder, and the rotation decreases stepwise. .

On the other hand, in the example of FIG. 7, a flat idle rotation can be realized up to a considerably high flow rate (up to a flow rate of A in FIG. 10). In this flow rate range, only the intake air flow rate used for calculating the basic injection pulse width Tp is limited to the maximum value Fqmax, and the fuel is not cut. Therefore, the amount of leakage air (from the control valve flow rate corresponding to the control valve command value, The air-fuel ratio becomes leaner as the outflow air amount increases), so the idle rotation does not change. Conversely, the characteristics of the curved portion in FIG. 9 are determined so that the idle rotation is constant even if the amount of leaked air increases.

As described above, in the example of FIG. 7, when the value of the gain G is smaller than the predetermined value (the range of G ≦ 6), the intake air flow rate used for calculating the supplied fuel amount instead of the fuel cut. Is limited to the maximum value. Therefore, unlike the example of FIG. 3, the range of the value of the gain G is small (that is, the actual flow rate Qs
(The range in which the deviation from the reference flow rate Pqmax falls within a predetermined value) can be reduced.

By the way, in FIG. 10, when the flow rate of A is equal to or more than the flow rate of A in the example of FIG. 7, the fuel cut is started, so that the rotation speed becomes saw-tooth like the example of FIG.

In this case, if it is desired to obtain a flat idle rotation up to a higher flow rate, the maximum value Fq of the above equation (6) is obtained.
max is further increased by a predetermined amount in synchronization with the fuel cut, and as a result, the amount of fuel injected into all cylinders is made substantially constant. Can be made flat.
For example, instead of the equation (6), the maximum value Fqmax is obtained by the equation of Fqmax = Pqmax × Qmxg × (the number of all cylinders / the number of non-fuel cut cylinders) (7).

It has been previously proposed that the intake air flow rate Qs used for calculating the supplied fuel amount is limited to a maximum value (Japanese Patent Application No. 4-347382). Since the engine stall limit is reached when the flow rate of A is exceeded, the control range is limited (FIG. 10).
Dashed line). On the other hand, in the example of FIG. 7, even if the control valve flow rate is very large, the idle speed control can be performed without engine stall.

[0061]

According to the first aspect of the present invention, the total flow passage area of the intake pipe is determined from the opening degree of the intake throttle valve and the command value to the control valve provided in the auxiliary air passage. While calculating the fuel injection amount based on the measured value of the intake air flow rate, and receiving the measured value of the intake air flow rate and the reference flow rate to determine whether the control valve has failed. However, when the control valve fails,
The measured value of the intake air flow rate deviates from the reference flow rate and increases.
The number of cylinders that cut the fuel supply from the fuel injection valve
In addition, since the fuel injection valve is driven according to the fuel injection amount when it is not at the time of failure, even if the large-capacity control valve is fully opened due to the failure, a flow limiting valve is required. Without increasing the idling speed and unnatural acceleration during running, etc., it is possible to use the full capacity of the large-capacity control valve, so the air flow control range of the engine can be expanded , Further sucking
The measured value of the incoming air flow rate is not related to the deviation from the reference flow rate.
Ru can keep the Ku engine rotation about the same.

According to a second aspect of the present invention, the total flow passage area of the intake pipe is calculated from the opening degree of the intake throttle valve and a command value to a control valve provided in the auxiliary air passage, and the reference flow rate is calculated from the total flow passage area. On the other hand, when the ratio is smaller than the predetermined value based on the result of determining whether the ratio between the measured value of the intake air flow rate and the reference flow rate is smaller or larger than the predetermined value, the gain set in accordance with this ratio and the reference flow rate are used. When the maximum value is calculated and the measured value of the intake air flow rate exceeds the maximum value based on a result of comparing the maximum value with the measured value of the intake air flow rate, the measurement of the intake air flow rate is performed based on the maximum value. When the value is equal to or less than the maximum value, the fuel injection amount is calculated based on the measured value itself, and when the ratio is smaller than the predetermined value from the determination result, the fuel injection valve is driven according to the fuel injection amount, and Is greater than the specified value Since that is configured to cut the fuel supply from the listening becomes the fuel injection valve, it is possible to suppress variation in the engine rotation than the first invention in a small area of said ratio.

[0063] The third aspect of the present invention is to increase the number of cylinders to cut the fuel supply as the above ratio becomes larger, in addition to the effect of the second aspect of the invention, regardless of the ratio of the above multi-cylinder engine, the first The engine speed can be kept substantially the same as in the invention of the first aspect.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a control system diagram of one embodiment.

FIG. 3 is a flowchart for explaining calculation of a fuel injection pulse width Ti.

FIG. 4 is a characteristic diagram showing a table of a throttle valve passage area Atvo.

FIG. 5 is a characteristic diagram showing a table content of a control valve passage area Aisc.

FIG. 6 is a table for explaining the details of fuel cut when a control valve fails.

FIG. 7 is a flowchart for explaining calculation of a fuel injection pulse width Ti according to a second embodiment.

FIG. 8 is a table for explaining the details of fuel cut when a control valve fails according to the second embodiment.

FIG. 9 is a characteristic diagram showing the contents of a table of gains Qmxg.

FIG. 10 is a characteristic diagram for explaining the operation of the two embodiments.

FIG. 11 is a conventional idle speed control system diagram.

FIG. 12 is a diagram corresponding to claims of the second invention.

[Explanation of symbols]

 1A, 1B Intake throttle valve 2 Auxiliary air passage 3 Flow control valve 4 Fuel injection valve 5 Control unit 6 Crank angle sensor 8 Throttle sensor (Throttle valve opening sensor) 9 Air flow meter (Air flow rate measuring means) 21 Intake throttle valve 22 Auxiliary Air passage 23 Flow rate control valve 24 Command value control means 25 Throttle valve opening sensor 26 Total flow area calculation means 27 Reference flow rate calculation means 28 Air flow rate measurement means 29 Injection amount calculation means 30 Injection valve driving means 31 Fuel injection valve 41 Ratio Calculation means 42 Size determination means 43 Gain setting means 44 Maximum value calculation means 45 Comparison means 46 Injection amount calculation means 47 Injection valve driving means

Continuation of front page (56) References JP-A-60-11648 (JP, A) JP-A-4-301160 (JP, A) JP-A-4-265437 (JP, A) JP-A-1-159153 (JP, A) , U) JP 7-72507 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 17/00-17/04 F02D 41/00-41/40 F02D 43/00 -45/00

Claims (3)

(57) [Claims] An auxiliary air passage that bypasses an intake throttle valve, a flow control valve that adjusts a flow rate of auxiliary air flowing through the passage according to a command value, and a command value to the control valve is controlled according to an operating condition. Means for detecting the degree of opening of the throttle valve, means for calculating the total flow area of the intake pipe from the detected value of the sensor and a command value to the control valve, and a reference based on the total flow area. Means for calculating the flow rate, means for measuring the intake air flow rate of the engine, means for calculating the fuel injection amount based on the measured value, and the control based on the measured value of the intake air flow rate and the reference flow rate Means for determining whether or not a valve has failed; based on the determination result, when the control valve has failed , the measured value of the intake air flow rate deviates from the reference flow rate and is large.
The cylinder that cuts the fuel supply from the fuel injection valve
Increasing the number, also when not in failure failsafe device auxiliary air control device which is characterized in that a means for driving the fuel injection valve in accordance with the fuel injection amount. 2. An auxiliary air passage for bypassing an intake throttle valve, a flow control valve for adjusting a flow rate of auxiliary air flowing through the passage in accordance with a command value, and a command value for the control valve being controlled in accordance with an operating condition. Means for detecting the degree of opening of the throttle valve, means for calculating the total flow area of the intake pipe from the detected value of the sensor and a command value to the control valve, and a reference based on the total flow area. Means for calculating the flow rate, means for measuring the intake air flow rate of the engine, means for calculating the ratio between the measured value of the intake air flow rate and the reference flow rate, and whether the ratio is smaller or larger than a predetermined value. Means for determining, means for setting a gain according to the ratio when the ratio is smaller than the result of the determination, means for calculating a maximum value from the gain and the reference flow rate, and measurement of the maximum value and the intake air flow rate Means to compare values From the comparison result, the fuel injection amount is determined based on the maximum value when the measured value of the intake air flow rate exceeds the maximum value, and based on the measured value itself when the measured value of the intake air flow rate is equal to or less than the maximum value. Means for calculating, and means for driving the fuel injection valve in accordance with the fuel injection amount when the ratio is smaller than a predetermined value, and for cutting off the fuel supply from the fuel injection valve when the ratio is larger than the predetermined value. And a fail-safe device for an auxiliary air control device. 3. The fail-safe device for an auxiliary air control device according to claim 2 , wherein the number of cylinders for cutting off the fuel supply increases as the ratio increases.